This is a double blind, placebo-controlled study to assess the safety, tolerability, and antiretroviral activity of DMP-266 in combination with open-label zidovudine (ZVD) and lamivudine (3TC) in HIV infected patients. The objectives of the study are : to evaluate the safety , tolerability and effectiveness (antiretroviral activity) of DMP-266 in combination with ZDV and 3TC in asymptomatic or mildly symptomatic HIV- infected patients; to assess the pharmacokinetics of multiple doses of DMP 266 in this patient population and to assess whether there is a pharmacokinetic interaction betweenZDV, 3TC and DMP-266; and to characterize the time course of development of resistance to DMP-266 and to characterize by genotyping and in vitro susceptibility testing strains of HIV resistant to DMP 266.